Choosing between using parametric and direct modeling can depend on your target product or product lifecycle needs. As Industry 5.0 rolls in, individual engineers and companies need options that enable quick concept exploration and product finalization. Understanding the two most common modeling approaches, parametric vs direct modeling, and their applications can help to decide which Computer-Aided Design (CAD) modeling approach to use for each stage of the product life cycle.
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Overview of Parametric vs Direct Modeling
At its core, parametric modeling is a combination of associative and solid or surface modeling that is feature-based while direct modeling is geometry-based. This key difference between parametric and direct modeling results in a separate set of rules for how to create and edit a model, impacting the speed of design, use, and application.
The rigor of parametric modeling stems from its development early in the Computer-Aided Development (CAD) scene in the 1980s when it replaced grueling calculations with automatic mathematical proofs. Direct modeling is a more recent type of modeling that has gained popularity for its flexibility and accessibility. This makes it a fit for the shorter development cycle and cross-collaboration needed in today’s manufacturing world.
At a glance, this is an overview of the degree to which each modeling type meets team and product development needs:
In parametric modeling, the geometries of a model are created piece by piece by adding features and connecting them to each other. Each feature, such as a circle, is directly defined using parameters, like diameter, that act as constraints. Each edit is recorded as a step, displayed in a feature tree timeline that creates a visual map of the design-build history. Each constraint and feature association added flows across the design, capturing design intent. Both creating and editing a model are time-intensive steps that require a lot of pre-planning and a level of proficiency typical to CAD experts in parametric modeling.
Direct modeling provides an alternative to parametric modeling, using geometry-based modeling. You can create and edit complex geometries simply by pushing, pulling, and twisting like modeling clay to get the shape and look you want. This approach results in achieving accuracy on par with parametric modeling. Each aspect of the model is free to move on its own independent of other geometries. Removing the need to search through the history of a model allows for more focus on conceptualization and design. Instead, drafting 2D drawings acts as the form of documentation for direct modeling.
Purpose & use of parametric and direct modeling
The stage of design or engineering phase can influence what type of modeling you use:
The pre-planning necessary for using parametric modeling contradicts the urgency of the conceptualization stage. This makes it less ideal than direct modeling for the conceptualization stage of a product. Using direct modeling, you can draft multiple concepts in parallel. The ability to check proportions, fine-tune as the concept evolves, and apply quick visuals enables rapid prototyping. This makes the bid and proposal process with initial concept design more efficient with the ability to edit designs quickly.
Executing detailed designs using direct modeling can result in faster development. Adjusting and layering details does not obstruct the coherency of the design as a whole for a more fluid design process.
For large-scale, detailed designs, importing into a parametric modeling environment for iterating designs like clearances and real-world simulation can help to finalize a product or structure. For a set range of products, using direct modeling through the end manufacturing process can result in a faster collaborative assessment. Adjusting final details with collaborative input can help to meet manufacturing criteria quickly and finalize your product.
The product uses of parametric vs direct modeling have different degrees of application.
Direct modeling is best used for:
- Rapid prototyping
The accessibility of creating geometry, checking proportions, and editing a design at any point in the design process makes direct modeling ideal for rapid prototyping.
- Machined parts
Machined parts, which are created using a cutting machine and used in the construction of larger parts, can be designed and modified efficiently using direct modeling. Coupled with Computer Numerical Control (CNC) machining, which enables the automated control of machine tools with computer software, rapid prototyping can be achieved along with an efficient system of production.
- Custom designs
The accessibility of the direct modeling method makes it suited for designers and engineers to custom-produce designs with the ability to adjust and refine designs to fit customer needs.
Parametric modeling is more relevant for designing large-scale or fine details of a project:
- Sheet metal
Sheet metal is a fundamental component of metalworking used in industrial processes and is bent and shaped to fit its purpose. The product applications of sheet metal span from aircraft frames to building fixtures. Using parametric modeling to model sheet metal used for larger bodies such as building faces can enable cost-efficient simulation due to the precision of associative relationships built up between features throughout the design process.
- Injection Molding
Using parameterized data helps to manage the highly complex nature of the plastic that makes up injection molds. Simulating the model pre-manufacturing helps to minimize error and reduce costs.
- High-complexity, large-scale assemblies
Given the associative relationships created that closely link features together, parametric modeling works to safeguard the integrity of complex assemblies.
Direct modeling advantages
The advantages of a direct modeling approach impacts the design process with wider applications for companies and stakeholders:
Faster concepting & design
The ability to interact directly with the geometry for flexible editing enables multiple concepts to be devised at a time for a more creative process. Designs can be adjusted and built upon quickly without sacrificing the integrity of the design.
Increased accessibility across teams
By making the design process more accessible and quicker to learn with direct modeling, the barrier of entry to creating CAD models is lowered. Instead of sorting through a modeling tree, designers are free to focus on fine-tuning design details. This increases interoperability across teams made up of a variety of disciplines by establishing a common understanding of CAD.
One-off design creation
The ability to access any part of the design independently of the rest allows for the creation of unique, customized designs.
Importing designs from a parametric modeling system can increase the pace of design and the ability to repurpose the design. Interacting directly with geometries without the need to reference a model tree increases the ability to scale the model per product needs.
Parametric modeling advantages
Long considered the gold standard for modeling, the parametric paradigm offers the following benefits:
Storing dimension definition
The ability to create and edit with parameter specifications of a feature makes the focus of dimension definition central to parametric design. The linking of features to create associative relationships prevents error in the design process and maintain model integrity.
With dimension definition, multiple parameters of each feature are established as a sequence of rules and features become dependent on one another. Whenever a parameter is edited, this change propagates along the entire design, resulting in high automation of parametric constraints that maintain the mathematical integrity of a model.
Model tree creation
The formation of a feature tree with each step executed in the design process charted creates a history of the product. The history-based format of parametric modeling makes the reuse of the design data by other designers possible so that the design can be revisited at any point during the product lifecycle.
Choose the modeling program that fits your workflow
Overall, parametric design takes years to learn and requires a daily commitment to maintain proficiency. A designer needs to visualize the model for pre-planning and manage feature dependencies to effectively navigate the design process. This high barrier to entry along with the rigid format can sacrifice speed and efficiency of concepting and designing.
Direct modeling fits the current needs of the manufacturing world to create high-quality products with a shorter development cycle. While parametric modeling ensures that the associative relationship between features is maintained for overall model integrity, the ability to ensure integrity of a model is not lost with direct modeling. Using direct modeling supports the construction of strong and stable models with a more accessible workflow.
Shapr3D uses direct modeling with a Siemens ParasolidⓇ geometric kernel. This combination allows for fast and precise calculation of geometric relationships that support the efficient creation of a visual mode. You can work from anywhere on Mac or iPad, Windows PC or tablet with multidevice integration. To learn more about our recently launched features, like Visualization and Shapr3D Cloud via Shapr3D Sync, click here.